Current state-of-the-art wheel dollies require their own hydraulic lift mechanism to ultimately raise the wheel from the floor. For example, U.S. Pat. No. 3,653,527 discloses a wheel dolly with an integrated hydraulic jack used to raise the wheel. Likewise, U.S. Pat. No. 4,050,597 discloses a similar jack system. The problem with these integrated jack systems is that they are heavy because of the additional weight from the dedicated jack system. They are also expensive for the same reason.
Other wheel dollies use a threaded bolt system to create the lift needed to raise the wheel. For example, U.S. Pat. No. 7,597,524 discloses a parallelogram lift system with a bolt that is turned to raise the wheels. U.S. Pat. No. 7,232,138 teaches a long bolt that, when turned, brings two arms in contact with the wheel, and, as the bolt is further turned, the arms lift the wheel. These systems, too, have shortcomings. It can be very taxing to turn a bolt sufficiently to raise a vehicle that weights several tons. Also, it can be unsafe to require a user to be so close to the wheel dolly with manual tools when lifting. Wheel dollies can fail for a variety of reasons, and a user should not be close to the dolly when such a failure occurs.
What is therefore needed is a wheel dolly that that overcomes these deficiencies.